A standard motor-vehicle door has welded-together inner and outer door panels or walls made of sheet metal and forming a central cavity that holds the latch and window parts which are inserted into the door through a hole in the inside wall. The inside wall is covered in use by a decorative panel.
As described in European patents 0,385,823 and 0,406,034 of Bertolini and in German patent document 4,407,114 of Hundertmark, the vehicle door latch is fixed to a holder that also carries the window operating mechanism. This entire unit is fitted to the door through the hole in its inside wall and is normally secured in place therein by screws. This holder carrying the door mechanisms is produced normally at one location and the actual door at another, and they are only united on assembly where the door is installed on the vehicle body and then the holder is fitted to the door.
Obviously such a system requires that the door and holder be manufactured to extremely close tolerances so that they fit together. Furthermore the door itself must fit perfectly in the vehicle body for the latch to operate. Clearly there are frequently circumstances where, due to manufacturing problems, the fit is not perfect and, as a result, the latch cannot function.
Another problem with these systems is that subsequent servicing of the latch, which is subject to considerable wear in normal use, is not possible. Instead the entire holder with all the other associated mechanisms must be replaced, greatly increasing the cost of what would otherwise be a simple repair.